1. Field of the Invention
The present invention relates to an organic light emitting display and a method for driving the same.
2. Description of Related Art
Recently, various flat panel display devices with reduced weight and volume in comparison to a cathode ray tube display device have been developed. Among the flat panel display devices, there are a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), an organic light emitting display, etc.
An organic light emitting display displays an image by using organic light emitting diodes (OLEDs) to generate light by the recombination of electrons and holes.
The organic light emitting display as described above has an excellent color reproducibility, a thin thickness, etc. so that its market has been largely expanded to a variety of applications such as applications in a PDA, an MP3 player, a cellular phone, etc.
An organic light emitting diode, which is included in an organic light emitting display, includes an anode electrode, a cathode electrode and a light emitting layer positioned therebetween. When current flows in a direction from the anode electrode to the cathode electrode, the light emitting layer emits light. Different luminances may be displayed by changing the amount of light emitted by varying the amount of current flowing from the anode electrode to the cathode electrode.
FIG. 1 is a schematic block diagram showing a conventional organic light emitting display. Referring to FIG. 1, the organic light emitting display includes a display unit 10, a data driver 20, a scan driver 30, and a power supply unit 40.
The display unit 10 includes a plurality of pixels 11 each including an organic light emitting diode (not shown). A plurality of n scan lines (S1,S2, . . . Sn−1, and Sn) extend in a row direction for transferring scan signals, a plurality of m data lines (D1,D2, . . . Dm−1, and Dm) extend in a column direction for transferring data signals, a plurality of m first power supply lines (not shown) for transferring a first power ELVDD, and a plurality of m second power supply lines (not shown) for transferring a second power ELVSS that has a lower potential than the first power ELVDD. The display unit 10 displays images by utilizing the organic light emitting diodes to emit light in response to the scan signals, the data signals, the first power ELVDD, and the second power ELVSS.
The data driver 20 applies the data signals to the display unit 10 through the data lines (D1, D2, . . . Dm−1, and Dm) that are coupled to the display unit 10.
The scan driver 30 sequentially outputs the scan signals to the scan lines (S1, S2, . . . , Sn−1, and Sn) to transfer the scan signals to a corresponding row of pixels 11 of the display unit 10. The row of pixels 11 of the display unit 10 receiving the scan signal are applied with the data signals from the data driver 20 to display the image, wherein all columns are sequentially selected so that one frame is completed.
The power supply unit 40 transfers the first power ELVDD and the second power ELVSS that has a lower potential than the first power ELVDD to the display unit 10 to supply a current corresponding to the data signals applied to the pixels 11 according to the voltage difference between the first power ELVDD and the second power ELVSS.
The organic light emitting display configured as described above allows a large amount of current to flow in the display unit 10 when displaying an image with a high luminance and a small amount of current to flow therein when displaying an image with a low luminance. When the large amount of current flows in the display unit 10 to display the image with a high luminance, a significant load is applied to the power supply unit 40 so that the power supply unit 40 should be capable of a high output current.